Performing nafl salaah with the intention of qadha for any salaah one may have missed

Q: Is it possible to make intention during nafl salaah that the nafl salaah be accepted for any qadha salaahs that one may have - specifically qadha salaahs that one may not be knowing of e.g. when ghusl after menstruation has been delayed or when a salaah may not have been performed in a state of wudhu unintentionally or one's ankles/hair may have been exposed, thus rendering salaah invalid?

Masbooq forgetfully making salaam with the Imaam

Q: I missed one rakaat of jamaat salaah. I would like to know if sajdah-e-sahw should be made or not in the following cases after the Imaam made salaam to end the salaah:

1. I made one salaam on the right and then stood up to complete the missed rakaat

2. I made both salaams on the right and left and immediately stood up to complete the missed rakaat

3. I made both salaams and sat in the same position, and after one minute I stood up to complete the missed rakaat.